The present invention is directed to an improved holding device for clamping or supporting in position carbon electrodes of a carbon arc lamp, particularly of the type employed in weathering testers.
There are presently known weathering testers of the type formed by a carbon electrode arc discharge lamp. In this type of device, a plurality of carbon electrodes are mounted in a lower support, and an equal number plurality of electrodes are mounted in an upper support directly above the lower electrodes. A frame of the device allows the lower electrodes and upper electrodes to be moved toward and away from each other. When the device is connected to a source of power, there are discharges across adjacent electrodes of the upper and lower groups, thereby creating light, whereby material positioned around the device may be weather tested.
In the past, the holder or support devices for both the upper and lower groups of electrodes have consisted primarily of a metallic element such as a copper alloy or stainless steel element presenting contact surfaces with a metallic coating, such as a copper coating, on each carbon electrode. However, although copper alloys have good electrical conductivity, they are easily oxidized and corroded, thereby decreasing the efficiency of the device. Stainless steel has a large contact resistance. Also, most metals are good conductors of heat and thereby excess heat is produced in the support or holder element.